In recent years, the use of a user terminal including a cellular communication unit and a wireless LAN communication unit (so-called dual terminal) is widely spread. Further, the number of wireless LAN access points managed by an operator of a cellular communication system increases.
Therefore, in 3GPP (3rd Generation Partnership Project) which is a project aiming to standardize a cellular communication system, consideration is given to a technology capable of strengthening cooperation between a cellular communication system and a wireless LAN system.
For example, when traffic transmitted and received between a user terminal and a cellular base station is transitioned to a wireless LAN system, it is possible to reduce the traffic load of the cellular base station (offload).
As a method of performing such an offload, there is proposed a method in which the cellular base station sets a WLAN measurement to a user terminal subject to offload, the user terminal reports a WLAN measurement result to the cellular base station, and then the cellular base station transmits an offload command to the user terminal on the basis of the report (see Non Patent Literature 1).